To use the 12mm tube friction/barb loss calculation tables for branching or split run laterals use the critical circuit length method shown below Critical circuit length example

The critical length of this circuit for the calculation is the

length of line A and the circuit's total flow and the length

of the longest water path which is line C and its individual

branch flow. Calculation for line A = 50' and total flow for

the circuit which is 6 g.p.h. x 17 emitters or 102 g.p.h.

In the .580 tubing table we would use the minimum 100' length

chart and 12.5 foot spacing column. Our total flow was 102

g.p.h. We would use the 105 g.p.h line and calculate a loss of

.936 p.s.i. for line A.

For line C we have 8 emitters at 6 g.p.h. for a total of 48

g.p.h. for flow. Line C is 100' long so

we use the 100 foot chart again, using the 55g.p.h. line to be

on the conservative side. In the 12.5 foot spacing column, we

read .316 p.s.i. loss at that flow.

The completed circuit calculation would be:

Line A .936 P.S.I. Loss

Line C +.316 P.S.I. Loss

1.252 P.S.I. Loss for the Entire Lateral

The flow and pressure for line B were accounted for in the

Line A calculation when the total flow of the circuit was

used. Then when we figured up the pressure needed at the tee

to supply the Digger branch, we automatically took care of the

smaller one.

Friction Loss Calculation For Branching PVC Laterals

There are at least two or three methods for determining

friction loss in branching PVC pipe laterals. The first, and

one of the most accurate, is the critical circuit length

method. Again, the critical circuit length is the longest path

that the water must travel in the circuit. With this method

for PVC pipe, the outlet factors are not used.

Step number one in this method is to determine the pipe

sections in the circuit that make up the critical path.

Step number two is to calculate the friction loss for the flow

of each of these sections beginning with the last section and

working back toward the head of the circuit.

Step three is to add up these losses for a total P.S.I.

friction loss number for the circuit. In circuits of 400, or

less, friction loss through the various fittings is

negligible. However, if you wish to throw in a very high,

conservative loss factor, add another 25% to your total pipe

friction loss number.

Step four is to add in any additional loss of pressure due to

elevation increases or subtract any elevation gains from your

total P.S.I. loss due to friction for your final number.

The second method for branching PVC laterals is the short cut

method where a certain degree of accuracy is sacrificed in

exchange for a fastball park estimate of friction loss.

With this method you assume that all the pipe in the lateral

is in straight line. Total up all the

pipe section in your lateral, then calculate the friction loss

as if the total flow of the circuit went the entire length.

Count up the number of outlets and select the closest

multiplier to your actual outlet number from Table 1. Next

multiply your P.S.I. loss by the outlet factor for your

estimate of pipe friction loss. Add 25% onto your pipe loss to

adjust for fitting loss and you then have your final P.S.I.

loss estimate.

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Parolical,Kottayam-686562,Kerala, ,

Phone:-0481-2792365